J/A+A/699/A251 Rotation-activity relationship and gyrochronology (Yang+, 2025)
Four ages of rotating stars in the rotation-activity relationship and
gyrochronology.
Yang H., Liu J., Soria R., Spada F., Wang S., Fang X., Li X.
<Astron. Astrophys. 699, A251 (2025)>
=2025A&A...699A.251Y 2025A&A...699A.251Y (SIMBAD/NED BibCode)
ADC_Keywords: Stars, activity ; Stars, ages ; Optical
Keywords: stars: activity - stars: chromospheres - stars: evolution -
stars: late-type - stars: rotation - stars: statistics
Abstract:
Gyrochronology and the rotation-activity relationship are
standard techniques to determine the evolution phase and dynamo
process of low-mass stars, based on their slowing down. Gyrochronology
identifies two tracks in color-period diagrams: the convective
(younger, faster rotating) and the interface (older, slower rotating)
phases, separated by a transition ('gap') without a precise estimate
of its duration. Instead, the rotation-activity relation identifies
two stages: the saturated (faster, with higher activity) and
unsaturated (slower, with declining activity) regimes. The mismatch in
the definition of the evolutionary phases has so far raised many
issues in physics and mathematics and hampered the understanding of
how the internal dynamo processes affect the observable properties.
To address this problem, we seek a unified scheme that shows a
one-to-one mapping from gyrochronology to the rotation-activity
relationship.
We combine LAMOST spectra, the Kepler mission and two open clusters to
obtain the chromospheric activity R'HK of 6846 stars and their
rotation periods. We use R'HK and rotation period to investigate the
rotation-activity relationship. Instead of the traditional
two-interval model, we apply a three-interval model to fit the
rotation-activity relationship in the range of the Rossby number
Ro<0.7. We also use the X-ray data to verify our new model.
We find that the rotation-activity relationship is best fitted by
three intervals in the rang of Ro<0.7. We associate those intervals to
the convective, gap and interface phases of gyrochronology. The mean
Ro of the C-to-g and g-to-I transition is ∼0.022 and ∼0.15,
respectively. The g-to-I transition is on the edge of the
intermediate-period gap, indicating that the transition of surface
brightness from spot-dominated to the facula-dominated can be
associated with the transition from gap to I sequence. Furthermore,
based on previous studies, we suggest an additional epoch at late
times of the I phase (Ro>0.7; weakened magnetic breaking phase) from
the perspective of activity. We further use the three-interval models
to fit the period-activity relationship in temperature bins and
determine the duration of the transition phase as a function of
effective temperature. By comparing the critical temperature and
period of the g-to-I transition with the slowly rotating sequence of
10 young open clusters whose ages range from 1Myr to 2.5Gyr, we
conclude that our new model finds the pure I sequence without fast
rotating outliers, which defines the zero-age I sequence (ZAIS). We
propose that there is an ambiguous consensus on when the I sequence
starts to work. This ambiguity is from the visually convergent
sequence of the color-period diagrams in open clusters. This visually
convergent sequence is younger than the ZAIS and is actually the pre-I
sequence that can be associated with the stall of the spin-down. Our
results unify the rotation-activity relationship and gyrochronology
for the stellar evolution of low-mass stars, for which we coined the
"CgIW" scenario.
Description:
We have combined LAMOST spectra with the Kepler mission and two open
clusters to obtain the chromospheric activity, R'HK, of 6846 stars
and their rotation periods.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tabler2.dat 157 6846 Data used in the study
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
V/156 : LAMOST DR7 catalogs (Luo+, 2019)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: tabler2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR3 Gaia DR3 ID
21- 28 I8 --- KIC ?=- Kepler input catalog ID
30- 38 F9.5 deg RAdeg Right ascension (J2000)
40- 48 F9.5 deg DEdeg Declination (J2000)
50- 54 A5 --- SpType Spectrum type given by the LAMOST pipeline
56- 59 I4 K Teff Effective temperature
61- 64 F4.2 [cm/s2] logg Surface gravity
66- 71 F6.3 [-] [Fe/H] Metallicity
73- 79 F7.4 --- Sindex Chromospheric activity in terms of the
Mount Wilson Observatory scale
81- 87 F7.4 --- e_Sindex rsm uncertainty of S-index
89- 94 F6.3 [-] log(R'HK) Normalized chromospheric activity
96-100 F5.3 [-] e_log(R'HK) rms uncertainty of log(R'HK)
102-107 F6.3 d Prot Rotation period
109-114 F6.2 d taug Global convective turnover time
116-121 F6.2 d e_taug rms uncertainty of the global convective
turnover time
123-127 F5.3 mag B-V Color index B-V
129-136 F8.3 Lsun Lbol ?=-999 Bolometric luminosity
138-144 A7 --- Phase Evolutionary phase (MS or post-MS)
146-157 A12 --- Cluster Field star (fs) or open cluster
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Acknowledgements:
Huiqin Yang, yhq(at)nao.cas.cn
(End) Patricia Vannier [CDS] 27-May-2025